Geometry

Points, Lines, and Shapes!

Plane

plane A flat surface that stretches into infinity.

Point

point A location in a plane or in space, having no dimensions.

Line Segment

line segment Two points on a line, and all the points between those two points.

Line

line A straight set of points that extends into infinity in both directions.

Ray

ray part of a line, with one endpoint, and extending to infinity in one direction.

Intersecting Lines

intersecting lines Lines that have one and only one point in common.

Parallel Lines

parallel linesTwo lines are parallel if they are in the same plane and never intersect.

Perpendicular Lines

perpendicular linesTwo lines are perpendicular if the angle between them is 90 degrees.

Angle

angleThe union of two rays with a common endpoint, called the vertex.

Acute Angle

acute angleA positive angle measuring less than 90 degrees.

Right Angle

right angleAn angle whose measure is 90 degrees.

Obtuse Angle

obtuse angleAn angle whose measure is greater than 90 degrees.

Straight Angle

straight angle An angle that measures 180 degrees.

Polygon

polygon A closed plane figure made up of several line segments that are joined together.

Triangle

triangle A three-sided polygon.

Triangles can be classified according to the measures of their angles and their sides.

Acute Triangle

acute triangleA triangle each of whose angles measures less than 90 degrees.

Right Triangle

right triangle A triangle that contains a right angle.

Obtuse Triangle

obtuse triangle A triangle with an obtuse angle.

Scalene Triangle

scalene triangleA triangle with no congruent (exactly the same size and shape) sides.

Isosceles Triangle

isosceles triangleA triangle with two congruent (exactly the same size and shape) sides.

Equilateral Triangle

equilateral triangleA triangle with all sides that are congruent (exactly the same size and shape).

Circle

circle The set of points in a plane that are a fixed distance from a given point, called the center.

Circle

circle The set of points in a plane that are a fixed distance from a given point, called the center.

Quadrilateral

quadrilateral Any four-sided figure is called a quadrilateral.

Parallelogram

parallelogram A quadrilateral with opposite sides parallel.

Rectangle

rectangle A parallelogram with four 90-degree (right) angles.

Square

square A parallelogram with four congruent (equal) sides and four 90 degree (right) angles.

Rhombus

rhombus A parallelogram with four congruent (equal) sides.

Opposite angles are congruent.

Trapezoid

trapezoid A quadrilateral that has exactly one pair of parallel sides.

The parallel sides are called bases.

The non-parallel sides are called legs.

If the legs have the same length, then the trapezoid is an isosceles trapezoid.

Isosceles Trapezoid

Isosceles Trapezoid

Kite

kite A quadrilateral that is shaped like a diamond. Sometimes people like to fly them!

It has two distinct pairs of adjacent (side-by-side) congruent sides.

Cylinder

cylindera solid figure that has two parallel bases that are congruent circles

Cone

conea solid figure that has a flat, circular base and one vertex

Cube

cubea solid figure with six congruent square faces

Square Pyramid

Square Pyramida solid figure with a square base and with four triangular faces that have a common point

Rectangular Prism

Rectangular Prisma solid figure in which all six faces are rectangles.

Rotation (turn)

Rotation (turn)a movement of a figure to a new position by turning it around a vertex

Reflection (flip)

Reflection (flip)a movement of a figure to a new position by flipping it over a line

Translation (slide)

Translation (slide)a movement of a figure to a new position along a straight line